This invention relates generally to the method of casting a metallic plate type heat exchanger as is used for the transfer of heat from one gaseous fluid to another.
In certain fields of application wherein corrosive or erosive gases are directed through such heat exchangers, cast iron is considered a preferred constituent inasmuch as cast iron has unique properties that effect resistance to corrosion and erosion from the gases.
Accordingly, U.S. Pat. Nos. 1,992,097, 2,537,276, and U.K. Pat. No. 1,197,409 are directed to various arrangements that utilized cast iron plates held in a spaced relation by a multiplicity of longitudinal bolts. The individual plates of the heat exchanger are first assembled by hand, bolts are inserted through holes in flanges at the sides of the plates, and fastening means such as nuts are then individually placed thereon and secured to provide a completely assembled envelope unit.
Gasket material such as pliable asbestos rope must be placed between envelope plates before they are bolted together to provide a satisfactory seal that precludes leakage of fluid between envelope plates.
Such a manufacturing process is slow and it requires excessive amounts of hand labor to assemble and properly join the separate elements of the heat exchanger into a leakage free unit. Moreover, the holes through abutting plates seriously weaken the plates to require additional reinforcement that adds even more to the cost and weight of the heat exchanger. An improvement in the casting process is disclosed in co-pending application Ser. No. 218,892 filed Dec. 22, 1980, wherein independent recuperator halves are cast separately and bonded together with molten metal along an imperforate peripheral flange that is common to both of the recuperator halves. While such a casting process as disclosed increases the strength of a completed unit and it substantially reduces the manufacturing time, cost and labor required to produce such as unit, the weight remains substantially the same, and the manufacturing process continues to be excessively time consuming and expensive.